Trusting the next step.

Enjoying life to the full – Taking carefree strolls through shopping centres, cycling with friends or perhaps going on a mountain hiking tour. With the right leg prosthesis being active can be part of  day to day life again. Ottoblock and maxon motor give people new quality of life.

Those who live with an amputation frequently have to overcome many hurdles on a daily basis – be it stairs or an uneven foot paths. With the right leg prosthesis, such hurdles are easy to overcome The C-Leg® is an intelligent leg prosthesis system that makes the life of transfemoral amputation patients much easier. With more than 40,000 supplied worldwide the advantages of this unique technology the C-Leg® prosthesis system are confirmed. Medical technology specialist Ottobock developed the leg prosthesis. Ottobock has shown stable growth for many years and as global leader in the field of prosthetics, it sets the benchmarks for the industry.
The company builds on the mature C-Leg® technology, which has proven itself time and time again since 1997. And up to today, C-Leg® is constantly being developed further. For the current model, which has been introduced into the market in July 2011, many developments have been implemented. The prosthesis is now certified for a max. body weight of 136 kg.
The intelligent knee joint permanently detects the current phase of the gait cycle and adjusts accordingly in realtime. The knee angle sensor supplies the information needed for dynamically controlling the swing phase, depending on the respective step length and frequency of the prosthesis wearer. The joint hydraulically limits the max. bending angle during the swing phase, i.e. when the leg prosthesis is in the air during the gait cycle. On the new C-Leg®, various mechanical and electronic adjustments allow improved swing phase control. As a result, the prosthesis user has a more natural gait and improved ease-of-movement in the knee joint. Whether the wearer is taking the stairs or manoeuvring through a packed shopping mall, taking a leisurely Sunday stroll or rushing to work – the C-Leg® system automatically adjusts to all situations. Uneven ground, darkness or a crowded environment is also no longer an insurmountable problem, as the high resistance secures the C-Leg® during the stance phase and the knee joint only switches to the swing phase when it is necessary.

This significantly reduces the risk of falling when wearing a leg prosthesis. The C-Leg® also offers a special mode that allows it to be configured for various activities such as cross-country skiing or cycling. In this additional activity mode, the amount of hydraulic dampening depends on the knee angle. The initial dampening and the progression can be configured individually. Thus the behaviour of the leg prosthesis can be programmed for diverse activities beyond normal walking.
To enable the prosthesis to withstand the stress to which it is subjected daily, the high-activity frame of the prosthesis is made of carbon, an extremely stable, high-quality and light material. The frame covers the electronics, the hydraulics and the battery.

What is behind it?
How exactly does the C-Leg® technology work? The intelligent controller of the prosthetic system adapts to the individual gait of each individual. The control operations are performed via a microprocessor-controlled hydraulic unit that dynamically adjusts the system to all gait speeds. Simultaneously the controller ensures that the prosthesis is reliably secured during the stance phase. This tried-and-tested control mechanism is achieved by means of a complex sensor system. The sensors record the load every 0.02 seconds, or, to be more precise, the sensors measure the ankle moments above the foot fitting component, as well as the angle and angle speed of the knee joint. Thus the knee joint permanently detects the current gait phase of the prosthesis wearer. A lithium ion battery powers the C-Leg® and lasts approx. 48 hours.

Small motor, large effect
The characteristics of the hydraulics are adapted by means of two valves. These valves are adjusted by maxon RE10 DC motors. Two motors are used in each C-Leg®. Here one of the main strengths of the RE10 is its compact size. With a diameter of just 10 mm, the motor is the second-smallest DC motor in maxon motor’s portfolio. This, combined with the CLL system for a long service life, played an important part in Ottobock’s decision to use these high-precision motors. The motors furthermore have ironless windings and neodymium magnets that allow top performance at a minimum size.

Precious-metal brushes are used for mechanical commutation of the motors. This ensures detent-free running of the maxon motors, even at low speeds. During commutation using brushes, contacts are constantly opened and closed via the inductive load of individual segments of the motor winding. The sparks generated when the contacts open attack the metal brushes and commutator of the motor, by melting the surface. This “brush fire” reduces the life span of the commutation system of the motor. By means of the capacitors integrated in the motors, the life span is significantly increased.

The CLL principle (capacitor long life) means that an additional element is inserted between two adjacent commutator segments, i.e. parallel to the opening contact. Through the use of the CLL concept, the brush fire is largely suppressed. Furthermore the spark reduction also has a positive influence on the electromagnetic radiation. In the C-Leg®, the maxon motors have to operate in pulse mode or intermittent mode, i.e. the motor is only activated for a short period for adjustments and is not constantly in use. Ottobock estimates that 9 million such adjustments are made during the life span of the C-Leg®. On average, the motor performs 10 rotations for these adjustments.

Taking a stand in life – on both legs
For many leg amputees, using the C-Leg® is a completely new experience. Contrary to other prostheses, the user of C-Leg ® do not have concentrate on every step. “It is not exhausting at all, it is impressively simple and I was really surprised. Now walking is fun again – almost like it used to be,” says Ed from America, who lost his leg in a car accident but has nevertheless been standing in a bakery for many years. The success story of the CLeg ® continues as more and more people are switching to this intelligent leg prosthesis and are achieving amazing things with it. In 2011, 74-year old Roland Zahn crossed Germany on foot, from Leipzig to Tübingen – with his C-Leg® as trustworthy companion. And a 60-year old woman climbed in the Himalayas at altitudes up to 4000 m with her prosthesis.

RE 10 DC motor

RE 10 DC motor

C-Leg® puts the joy back in walking
C-Leg® puts the joy back in walking

About maxon motor Australia

maxon motor is the world’s leading supplier of high-precision drive systems. More than 40 years’ experience, constant innovation, top-quality products and competent customer service make maxon motor a reliable partner in the drive technology sector. We are driven by your specific requirements. The product range incorporated in the modular system is comprehensive: Brushed and Brushless DC motors with the unique ironless maxon winding Flat motors with iron cores Planetary gears, spur gears and special gears Sensors (encoders, DC tachos, resolvers) Servo amplifiers, position controllers and control electronics High-tech CIM and MIM components Customer specific drive solutions. maxon motor is a Swiss company headquartered in Sachseln (Central Switzerland) that employs more than 2000 staff worldwide. With 14 sales companies based in over 30 countries, sales partners in another 10 countries and with six production sites, maxon motor are able to provide locally-based and competent customer service. maxon motor helps provide innovative solutions at competitive prices for numerous applications in various markets, such as Medical technology, Industrial automation and robotics, Aerospace industry, Automotive industry, Communication, Consumer applications, Inspection and Instrumentation and Safety engineering. maxon motor Australia is based in Mt Kuring-Gai NSW and our staff will be happy to help you with all your DC motor and technical enquiries.

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